Yes, the AIDL interfaces on the Server and on the Clint sides must be synchronized. AIDL file is just an interface the implementations of which on the client and server side are generated during the compilation of your client and server code. This interface defines how to marshal the calls from client to server, thus, if your interfaces are not synchronized on the client and on the server you'll get the problems in marshalling calls (this is the problem you see in your case).
It is better to create a library that contains the AIDL interface as a separate project and attach it to your client and server projects. Thus, you'll have the same AIDL interface for both projects.